Acrylonitrile styrene acrylate

Acrylonitrile styrene acrylate (ASA), also called acrylic styrene acrylonitrile, is a thermoplastic developed as an alternative to acrylonitrile butadiene styrene (ABS), but with improved weather resistance, and is widely used in the automotive industry. It is used for general prototyping in 3D printing, where its UV resistance and mechanical properties make it an excellent material for use in fused deposition modelling printers. Acrylonitrile styrene acrylate (ASA), also called acrylic styrene acrylonitrile, is a thermoplastic developed as an alternative to acrylonitrile butadiene styrene (ABS), but with improved weather resistance, and is widely used in the automotive industry. It is used for general prototyping in 3D printing, where its UV resistance and mechanical properties make it an excellent material for use in fused deposition modelling printers. ASA is structurally very similar to ABS. The spherical particles of slightly crosslinked acrylate rubber (instead of butadiene rubber), functioning as an impact modifier, are chemically grafted with styrene-acrylonitrile copolymer chains, and embedded in styrene-acrylonitrile matrix. The acrylate rubber differs from the butadiene based rubber by absence of double bonds, which gives the material about ten times the weathering resistance and resistance to ultraviolet radiation of ABS, higher long-term heat resistance, and better chemical resistance. ASA is significantly more resistant to environmental stress cracking than ABS, especially to alcohols and many cleaning agents. n-Butyl acrylate rubber is usually used, but other esters can be encountered too, e.g. ethyl hexyl acrylate. The latter has lower glass transition temperature than the former, -65 °C vs -45 °C, providing better low-temperature properties to the material. ASA has high outdoor weatherability; it retains gloss, color, and mechanical properties in outdoor exposure. It has good chemical and heat resistance, high gloss, good antistatic properties, and is tough and rigid. It is used in applications requiring weatherability, e.g. commercial siding, outside parts of vehicles, or outdoor furniture. As of 2003, there were only few large manufacturers of ASA; e.g. BASF, General Electric, Bayer, Miele, Hitachi, and LG Chem. The production process is similar to ABS, but it has some key differences and difficulties. The annual demand around 2003 was about 1-5% of ABS. In the Fused Deposition Modeling 3-D printing process, the ASA filament is used to fabricate 3-D printed parts, which above all must absorb a certain amount of impact and impact energy without breaking. ASA is compatible with some other plastics, namely polyvinyl chloride and polycarbonate. ASA-PVC compounds are in use. ASA can be processed by extrusion and coextrusion, thermoforming, injection molding, extrusion blow molding, and structural foam molding. ASA is mildly hygroscopic; drying may be necessary before processing. ASA exhibits low moulding shrinkage.